diff --git a/app/models/user_password_reset_nonce.rb b/app/models/user_password_reset_nonce.rb
index 74dba55c4..55a32a12c 100644
--- a/app/models/user_password_reset_nonce.rb
+++ b/app/models/user_password_reset_nonce.rb
@@ -5,7 +5,7 @@ class UserPasswordResetNonce < ActiveRecord::Base
   after_create :deliver_notice
 
   def self.prune!
-    destroy_all(["created_at < ?"], 1.week.ago)
+    destroy_all(["created_at < ?", 1.week.ago])
   end
 
   def deliver_notice